The present invention relates to a process for utilizing waste waters which comprises the separate collection of gray water and/or black water and membrane filtration of the separately collected gray water and/or the solids/liquid separation of the separately collected black water. The present invention preferably relates to a process of producing potable water from gray water or from one or more of its partial streams. Moreover, an apparatus for producing potable water from gray water and an apparatus for utilizing black water and its use are described.
The present method comprises the treatment and recycling of the separately collected individual waste water streams of gray water and black water, which is preferably divided into faecal waste water and urinal waste water and can be separately collected, in order to thus provide a precondition for a highly efficient water management in regions with water problems.
The process is preferably based on the separate routing of black and gray waters and also preferably on the use of water-saving toilets.
The gray water can be used to produce potable water. The individual partial gray water streams can be pretreated separately and used to produce potable water. One aspect of the process is the use of sea water desalinization plants in the treatment of gray water. The effects achieved in the desalinization plant are not only a substantial removal of residual substances and simultaneous sanitation, but also a great reduction of the osmotic pressure.
The basic idea underlying the process is the maximization of the mineral fertilizer concentration by open liquid circulation by collecting the waste water together with the organic waste fraction in the discharge of waste water treatment plants.
The nutrients of the urinal waste water can be separately collected by separation toilets and urinals and can be anaerobically recovered. The black or faecal waste water is oxidized to nitrification and is reused to flush toilets and urinals, and is thus only used as a transportation means, in which the nutrients can be concentrated and discharged. Moreover, nitrate can be used as a flotation aid of the solids in the anaerobic first solids/liquid separation. In the case of composting, there is an additional cycle. This liquid cycle starts with the irrigation of the compost with the effluent from an aerobic waste water treatment step. The nutrients released by composting are thus washed away and concentrated in the outlet of the waste water treatment plant by irrigation water supplied to the aerobic treatment step. Suitable measures to greatly prevent denitrification can also be taken depending on the process variant. The theoretically smallest discharge volume of about 2 l/(PE*d) and the thus possible drying of the mineralized nutrient enables treatment without difficulties and odorless recycling of the nutrients into the nutrient cycle.
Bio waste is processed together with any resulting sludges in order to produce bio gas and compost.
The starting substrates
Definitions
Waste and dirty waters are the sum parameters of all types of individual waste streams of industrial or domestic origin. The following individual waste water streams are of particular interest here:
Faecal waste water is defined as waste water which is only laden with feces (for instance from the feces outlet of urine separation toilets); other waste waters of similar composition stemming from other sources can be admixed here.
Urinal waste water is defined as waste water which is only laden with urine and stems from all kinds of urinals and/or from the urine-laden outlet of urine separation toilets; in this case, too, other waste waters of similar composition stemming from other sources can be admixed.
Black water is defined as waste water laden with both urine and feces, for instance from all kinds of toilets and urinals. Urinal waste water and/or faecal waste water can be drained and collected in a separate sewerage net. Moreover, the black water and/or its partial streams of urine waste water and faecal waste water can be received in surges in the same sewerage nets, and treated separately. In cases of particular similarity regarding pollution parameters, other waste waters from agriculture (for instance liquid pig manure) and/or from other sources can be admixed.
Gray water is defined as domestic waste water which is not or hardly laden with urine and/or feces and/or is defined as other waste water of similar composition stemming from laundries and/or other sources, which can be received in one or several separate sewerage nets. According to its origin and/or composition it can be subdivided into several grey water partial streams. The gray water can be composed of all conceivable combinations of all conceivable numbers of domestic and similar waste water sources, but must not contain black water (feces and/or urine), although a portion of faecal and/or urinal waste water admixed to one or several partial streams of the gray water does not make a difference to this definition.
Toilet as used herein is the general term for all types of toilets. Toilets with water supply can be divided into flush toilets and water-saving toilets.
Flush toilets are conventional toilets which are commercially available today and may also be equipped with water-saving devices (for instance a water saving key).
Water-saving toilets are special constructions with a high water saving effect, such as for instance vacuum toilets, urine separation toilets, etc.
Urinals are all types of separate urine outlets with or without water flushing, as for instance simple runs, urinals with individual or automatic water flushing, water-free urinals, etc.
Bio waste is defined as solid, biologically degradable waste products which may contain biologically inert components.
Carbon as used herein is defined as referring to all organic carbon compounds (CSB and BSB) which may be contained in black and gray waters and in bio waste. It may also refer to carbonates.
Nitrogen as used herein is defined as referring to all organic and inorganic nitrogen compounds which may be contained in black water and gray water and in bio waste.
Phosphorus as used herein is defined as referring to all organic and inorganic phosphorus compounds which may be contained in black water and gray water and in bio waste.
Filtration covers all coarse screen and/or fine screen filters and/or membrane (filtration) methods that can be used in waste water purification and potable water recovery. It includes all filtration and/or membrane methods known to the a skilled person, such as ultra or microfiltration, which are for instance described in the ATV volumes, Ulmann""s Enzyklopxc3xa4die, and other technical literature and technical journals, for instance Korrespondenz Abwasser, etc., and/or available on the market. Furthermore, process-enhancing additives may be added.
Solids/liquid separation covers all separation processes of liquid and solid materials which can be used in domestic waste water purification and potable water recovery, as e.g. sedimentations, and which are suitable (hydrocyclone classifiers, for example, do not lend themselves to solids/liquid separation in larger people equivalents connection sizes). For instance all types of filtration processes including reverse osmosis and/or other membrane processes for solids/liquids separation can be used. They include all processes for solids/liquid separation known to a skilled person, such as for instance adsorption processes, precipitation, filtration and membrane processes, dedimentation and flotation processes etc., which are for instance described in the ATV volumes, Ullman""s Enzyklopxc3xa4die and other technical literature and technical journals, e.g. Korrespondenz Abwasser etc, and/or available on the market. Furthermore, process-enhancing additives may be added.
Fixed bed processes cover all processes in which microorganisms grow sessily on a fixed and/or mobile matrix, such as trickling filters, RBC (rotating bio contactor) filters and rotating discs, all types of soil filters, fluidized bed processes, sand filter, planted soil filters etc. They include all processes that are known to a skilled person, which are for instance described in the ATV volumes, Ullman""s Enzyklopxc3xa4die and other technical literature and technical journals, e.g. Korrespondenz Abwasser etc, and/or available on the market. Process-enhancing additive may also be added.
Activated material processes comprise all processes in which microorganisms float freely in the liquid to be treated, such as for instance activated sludge processes, SBR (sequencing batch reactor) plants etc. They include all microorganism-based oxidation processes which are known to a skilled person and are for instance described in the ATV volumes, Ullman""s Enzyklopxc3xa4die and other technical literature and technical journals, e.g. Korrespondenz Abwasser etc, and/or available on the market. Process-enhancing additive may also be added.
Oxidation by microorganisms, aerobic treatment step and wet oxidation are synonyms within the meaning of the present invention and are the generic terms of oxidative fixed bed and activated material processes and other nature-resembling processes. They include all processes that are known to a skilled person, such as microorganism-based oxidation, which are for instance described in the ATV volumes, Ullman""s Enzyklopxc3xa4die and other technical literature and technical journals, e.g. Korrespondenz Abwasser etc, and/or available on the market. Process-enhancing additive may also be added.
Removal carbon covers all processes for removing carbon from a liquid. It comprises all processes which are known to a skilled person, such as microorganism-based oxidation, e.g. adsorption processes, e.g. precipitation processes and e.g. chemical oxidation processes, etc, which are for instance described in the ATV volumes and other technical literature and technical journals, e.g. Korrespondenz Abwasser etc, and/or available on the market.
1.2 Comparison of the domestic waste water partial flows
Most people know little about the dirty water produced by our civilization. As a rule, they do not know that it can be composed of very different xe2x80x9cwaste watersxe2x80x9d. Within the meaning of this invention the term xe2x80x9cpartial stream of waste waterxe2x80x9d and the term xe2x80x9cpartial streamxe2x80x9d are used as synonyms.
The following Table 1 is a compilation of the approximate distribution of black and gray water components. The columns xe2x80x9cblack waterxe2x80x9d and xe2x80x9cgrey waterxe2x80x9d show the percentage distribution of the waste water components.
The values indicated in Table 1 are maximum values which may vary in individual cases. The existing studies are not significant enough. Table 1 shows how little sense it makes to mix black water with gray water. In the case of lack of nutrients in gray water, or in any combination of partial streams of gray water, a part of the oxidized nutrients of the black water can be added for complete carbon degradation.
Table 2 shows the sources from which the individual loads of material come.
Table 2 shows the different loads of carbon, nitrogen and phosphorous from the sources xe2x80x9cgray waterxe2x80x9d, xe2x80x9cfecesxe2x80x9d and xe2x80x9curinexe2x80x9d. The different load profile which the feces and urine sources have in respect of the carbon and nitrogen parameters justifies separate collection and/or treatment of the urinal waste water.
Black water
As mentioned before, waste water from toilets and urinals is termed black water. It is composed of feces, urine and water. Urine contains more than 80% of daily produced human nitrogen (urea) dissolved in water. Feces contain about 50% of the daily produced human carbon in solid form and more than 50% of the phosphorus and 10% of the nitrogen. Almost the whole range of pollutants can be found here: carbon, phosphorus and potassium primarily in the feces, nitrogen mainly in the urine. Moreover, black water contains pathogenic bacteria from the human intestinal tract (so-called coliform bacteria). The bacteria which are contained in the sedimented sludge, can be completely killed by subsequent fermentation and composting, the bacteria contained in the water must be sterilized to be killed completely.
Regarding quantity, black water amounts to about 30% of the total domestic waste water. However, this quantity can be reduced to less than 15% by the choice of suitable water-saving toilets. Here, the calculations should always be checked correctly. The construction costs and operation costs of the process could be dramatically reduced by the separation of the black water, but it is necessary to install a second sewerage net. However, since it can be installed in parallel with the sewerage net that must be installed anyway, only the costs for the pipes and minor additional costs for the construction of the conduit net arise in addition.
From a scientific point of view, feces and organic waste consist of the substances, life consists of: They primarily consist of carbon (C), oxygen (O), hydrogen (H), nitrogen (N), sulfur (S) and phosphorus (P), but also of a whole range of trace elements, such as for instance potassium (K). Here, the compositions vary depending on nutrition habits and/or economic conditions. Primarily carbon, nitrogen and phosphorus are environmentally relevant for water pollution. They are produced in an energy-intensive form and are expensively removed from the water by conventional sewage treatment plants.
Carbon is biologically converted in water into CO2 by bacteria in the presence of oxygen. Thus, a great amount of oxygen is used up in this conversion. One consequence of this is that the fish in the water suffocate. Plants are able to assimilate and utilize the thus formed CO2 from the air. Hence, carbon is not a fertilizer.
Nitrogen, phosphorus and potassium are factors in short supply in plant growth and are thus the main components of fertilizers. Potassium is environmentally inert in water, while nitrogen and phosphorus may lead to an explosion-like algae growth in waste water. Algae are also plants and thus assimilate carbon from the air, and in the presence of nutrients thus lead to a carbon-enrichment in water, which leads to the development of catabolic food chains and to a great oxygen depletion of water and thus to the death of fish. The term used is the water has xe2x80x9cturnedxe2x80x9d or xe2x80x9ceutrophiedxe2x80x9d.
The nutrients are suitable fertilizers for agricultural use. Commercial mineral fertilizers inter alia consist of saltpeter (KNO3) and phosphate (PO4). Exactly these substances are produced by the process and may be returned in solute or solid form to the production.
Gray water
Gray water is the waste water from all other domestic sources (see the definitions above), such as showers, wash-basins, washing machines, kitchen waste water etc. Gray water is practically nitrogen-free and phosphorus-free; hence it can be purified to highest quality with relatively little expenditure.
Waste water from dish-washers is usually allocated to gray water, but should be directed to black water because of its composition of pollutants.
The pollution of gray water compared to that of black water is minor and can be purified with relatively little expenditure. Gray water contains nitrogen impurities only in very low trace amounts and is considered to be practically free from phosphate, as predominantly phosphate-free detergents are used nowadays.
Gray water amounts to about 70 to 80% of the daily waste water produced and accounts for the largest quantity and is particularly suitable for recycling for the following reasons:
1. it is not contaminated with coliform bacteria
2. it involves no ethical problems for the consumer of potable water
3. it shows a low carbon pollution
4. it shows a minimum nitrogen and phosphorus pollution.
The production of potable water from gray water is particularly worthwhile for communities in countries where potable water is in short supply, as for instance in the Maledive Islands, where 1 m3 of potable water now costs more than 6 US $.
Bio waste
The amounts of bio waste vary considerably. For instance the amount in German communities is only about 200 g per inhabitant and per day, but is more 1.2 kg per day in Asian hotels. Bio waste contains the residual quantities of nitrogen and phosphorus not contained in black water.
Prior art
Control sewage treatment plants and centralized sewerages
Sewage treatment plants which purify waste waters that is to say which expensively remove waste water components and direct the purified water via rivers to the sea represent the state of the art. Hence, this water is admixed with salt and withdrawn from the fresh water cycle. In regions where water is in short supply, fresh water is for instance produced by sea-water desalinization plants where the process of the present invention offers an inexpensive alternative. The prior art covers a linear flow through technique and essentially suffers from the following drawbacks:
1. The most different types of waste waters from commerce, industry and households are admixed. Rain water is often also directed to the combined sewage system. The consequences of this admixture are that
recovery and recycling of the nutrients from black water is impossible because of their admixture with poisonous industrial waste waters;
for the same reason, a poisonous sewage sludge is formed
low-salt waste waters are directed to the sea via the surface water collectors and thus fresh water is wasted, producing considerable costs especially in regions where water is in short supply;
the low concentration of the waste water components requires their technically sophisticated and expensive removal;
non-purified waste waters are washed out by rain peaks.
2. Inflexibility of centralized systems. A rigid system cannot react swiftly to rapid changes in the requirements, as for instance in the booming touristic areas.
Decentralized separation of black and gray waters
Historically, black water was treated separately especially in Asia. In this connection, especially the bio gas plants of India and China and the xe2x80x9cNightsoilxe2x80x9d treatment methods of Japan and Korea are to be mentioned. The process variations can be described as follows:
a) Heat treatment process
After coarse particle removal, the black water is passed to a quantitative equalization tank. After heating and subsequent solids/liquid separation, the black water is diluted with fresh water in a ration of 1:20, and subjected to an activated sludge process.
b) Anaerobic treatment (anaerobic digestion process)
After coarse particle removal and quantitative equalization, the black water is subjected to a two-stage anaerobic process and after subsequent solids/liquid separation is diluted with fresh water in a ratio of 1:20, and directed to an activated sludge process.
c) Aerobic process aerobic digestion process)
After coarse particle removal and quantitative equalization, the black water is subjected to aerobic treatment, and after subsequent solid/liquid separation the black water is diluted with fresh water in a ratio of 1:20, and subjected to an activated sludge process.
d) Two-stage activated sludge process
After coarse particle removal and quantitative equalization, the black water is diluted with water in a ratio of 1:10 and treated in a first activated sludge process. After subsequent solids/liquid separation the black water is again diluted with fresh water in a ratio of 1:10, and subjected to a second activated sludge process.
In recent times, the separation of black and gray water has been reduced to practice only in Norway and in the Federal Republic of Germany and only in a few projects.
e) Gray water processing
In Norderstedt, near Hamburg, black and gray waters were collected separately. The gray water is processed in a one-stage procedure, and just as the untreated black water, is then directed to a combines sewage system. The drawbacks of this process concept are the following aspects:
Gray water processing at best allows its reutilization as flush water for toilets and urinals.
The introduction of untreated black water makes it impossible to close the nutrient cycle.
f) Fermentation of black water and bio waste
At present, Lxc3xcbeck plans a residential area in which black water is separated from gray water. It envisages fermentation of the total black water with bio waste and subsequent use of the fermentation broth in agriculture. The unfavourable C:N ratio is to be counteracted by an increase of the active bio mass in the anaerobic reactor. The drawbacks of the process in particular in the use in touristic areas with short water supplies are the following aspects:
Odorless application of the nutrients in the vicinity or on touristic grounds (for instance golf courses, parks, public gardens etc.) is not possible.
With a previous solids/liquid separation step, the volume of the bio gas plant could be reduced to about a fourth while operation stability could at the same time be increased because of the improved C:N ratio.
Water-saving in the toilet sector is only possible via the use of water-saving toilets, given the absence of a black water cycle.
g) Fermentation of black water and bio waste
A pilot plant for the solar residential area xe2x80x9cam Schlierbergxe2x80x9d working according to the same process as that of Lxc3xcbeck (see below) was put into operation in Freiburg in May 1997. During the test phase, acidification tendencies on account of the too low C:N ratio were reported. Following the test results, the process according to FIG. 3 was modified end of 1997 by the engineers working on this project. The drawbacks of this process when used in touristic areas suffering from short water supplies are the same as in the case of the previously discussed process.
h) Aerobic black water oxidation
An aerobic thermophilic oxidation plant for total black water has been built in Norway near Oslo. The drawbacks of this process are the high energy consumption of the CSB fraction and the absence of bio gas production.
The processes known in the art are, however, inadequate for many waste water removal or utilization areas. Hence, it is an object of the invention to provide an improved process for waste water utilization. This object is achieved by the embodiments specified in the claims.
Thus, the invention relates to a process for utilizing waste waters, which comprises the following steps:
(a) separate collection of gray water and/or black water; and
(b) membrane filtration of the gray water separately collected in (a) and/or solids/liquid separation of the black water separately collected in (a).
In a preferred embodiment of the invention, the process for producing potable water from gray water or from one or more of its partial streams comprises the following steps:
(a) separate collection of gray water or one or more of its partial streams; and
(b) membrane filtration of the gray water separately collected in (a) or one or more of its partial streams.
In a particularly preferred embodiment, membrane filtration is carried out by reverse osmosis or ultra- or microfiltration.
In another particularly preferred embodiment the ultra- or microfiltration is followed by a desalinization step.
In another particularly preferred embodiment, membranes having a pore size of at the most 2 xcexcm are used for ultra- or microfiltration.
In another particularly preferred embodiment, membranes having a pore size of at the most 0.2 xcexcm are used for ultra- or microfiltration.
In another particularly preferred embodiment, one or more mechanical, physical and/or chemical purification steps precede (b).
In another particularly preferred embodiment the process according to (a) comprises the following steps:
(i) solids/liquid separation; and/or
(ii) carbon removal
In another particularly preferred embodiment step (ii) is followed by solids/liquid separation.
In another particularly preferred embodiment, solids/liquid separation is carried out by flotation, sedimentation, filtration or precipitation.
In another particularly preferred embodiment, carbon removal is carried out by oxidation with the use of microorganisms.
In another particularly preferred embodiment, the process of invention comprises the following step subsequent to (b):
(c) sanitation and/or modification of the water structure of the gray water or one or more of its partial streams recovered in (b).
In another particularly preferred embodiment, sanitation is a treatment with chlorine.
In another preferred embodiment of the invention, black water utilization comprises the following steps:
(a) separate collection of black water from toilets with or without urinals;
(b) solids/liquid separation of the black water collected in (a);
(c) oxidation by microorganisms of the liquid phase recovered in (b);
(d) solids/liquid separation of the product obtained in (c);
(e) utilization of the liquid phase obtained in (d) (ea) for collecting black water according to (a); and/or (eb) as a mineral fertilizer; and
(f) optional repetition of steps (a) to (ea) one or more times.
In a particularly preferred embodiment, the black water is separately collected in step (a) as faecal and urinal waste waters and the faecal waste water is treated according to steps (a) to (f).
In another particularly preferred embodiment of the invention, at least a part of the urinal waste water is added to the faecal waste water before step (c).
In another particularly preferred embodiment of the invention, the solids/liquid separation in (b) is a flotation process in the event that steps (a) to (ea) are repeated one or more times.
In other particularly preferred embodiments of the invention, one or more mechanical, physical and/or chemical purification steps precede step (c).
In another particularly preferred embodiment of the invention, the solids/liquid separation in (d) is a filtration process.
In another particularly preferred embodiment, the solids/liquid separation in (b) is a sedimentation or filtration process.
In another particularly preferred embodiment, the product from (d) is intermediately stored in a storage tank and in the case of a higher performance demand, is supplied again to the oxidation equipment under increased air supply.
In another particularly preferred embodiment, the oxidized black water and/or faecal waste water is subjected to sanitation prior to reutilization and/or to a modification of the water structure.
In another particularly preferred embodiment, the solids are removed from the urinal waste water by filtration.
In another preferred embodiment, the solids from the gray water and/or the black water and/or faecal waste water are subjected to a one or two-step anaerobic fermentation process together with or without fragmented bio waste.
In another particularly preferred embodiment, the potable water is filled into containers.
In another particularly preferred embodiment, the mineral fertilizer and/or compost is filled into containers.
Moreover, the invention relates to an apparatus for carrying out the process of the invention which comprises a reactor in which steps (b), (c) and (d) are carried out.
The apparatus according to the invention comprises membranes as explained above, as well as a mixer, an aerator, a scum offtake, and optionally other components.
In another particularly preferred embodiment, the apparatus comprises a separator in which the process steps characterized in the process of the invention are carried out.
Furthermore, the invention relates to the use of the apparatus of the invention for utilizing black water.
In another embodiment, the invention relates to the use of the apparatus of the invention in order to produce potable water from gray water.